1. Field of the Invention
The present invention relates to a two-cycle internal combustion engine capable of directing injection of an air-fuel mixture into a combustion chamber while preventing blowby of the air-fuel mixture. This injection of the air-fuel mixture in the present invention reduces fuel consumption and improves exhaust gas purifying performance.
2. Description of Background Art
In a related art two-cycle internal combustion engine, fuel supplied from a carburetor or the like is mixed with intake air, and the air-fuel mixture is sucked in crank chamber and supplied to the combustion chamber through scavenging openings. In this related art engine, since the timing of the opening of the exhaust opening is set earlier than the timing of the opening the scavenging openings (an upper edge of the exhaust opening is higher than upper edges of the scavenging openings), exhaust of the air-fuel mixture supplied in the combustion engine into the exhaust opening, i.e., "blowby" can occur.
The blowby phenomenon is suppressed by an exhaust pulsation effect; however, it is difficult to suppress the blowby over the entire operational range. As a result, the blowby increases fuel consumption and decreases exhaust gas purifying performance.
Two-cycle internal combustion engines intended to solve the above-mentioned problem have been disclosed in Japanese Patent Laid-open Nos. Hei 3-100318 and Hei 5-302521. In the two-cycle internal combustion engine described in Japanese Patent Laid-open No. Hei 3-100318, a high pressure chamber is connected to a crank chamber through a check valve. The high pressure chamber is connected to a combustion chamber through an air passage and a solenoid valve is interposed at a lower end of the air passage. Furthermore, a fuel injection valve for injecting fuel in the combustion chamber is provided at an upper end of the air passage. In the two-cycle internal combustion engine described in Japanese Patent Laid-open No. Hei 5-302521, a chamber portion is disposed adjacent to the crank case and the cylinder block, an intake control valve is interposed between the crank chamber and the chamber portion, a scavenging control valve is interposed between the chamber portion and the combustion chamber in the cylinder; and a fuel injection valve for injecting fuel in the chamber portion is provided.
The two-cycle internal combustion engine described in Japanese Patent Laid-open No. Hei 3-100318 has a problem, however. Since the fuel supply opening is provided in a side wall of the cylinder at a position facing the combustion chamber and the fuel injection valve is disposed directly perpendicular to the fuel supply opening, sprayed fuel collides with the cylinder wall on the exhaust opening side which is opposed to the fuel supply opening. Therefore, the sprayed fuel can adhere to the cylinder wall.
If the fuel spraying timing is set to be earlier in order to prevent interference between the piston and the sprayed fuel, the sprayed fuel tends to be blown-by through the exhaust opening. If the fuel supply opening is disposed at a higher position to delay the fuel spraying timing, the fuel injection valve is directly exposed to the combustion gas at a high temperature, the injection valve to require a high thermal resistance.
Furthermore, in the two-cycle internal combustion engine described in Japanese Patent Laid-open No. Hei 5-302521, since an air-fuel mixture injected from the scavenging control valve is supplied into the combustion chamber through all of the scavenging openings, the blowby of the air-fuel mixture from the exhaust opening cannot be avoided.
In the two-cycle internal combustion engine in which fuel is directly injected into the cylinder, the direction of the sprayed fuel is generally very important, since if the direction degrades, short-cut of sprayed fuel through the exhaust opening occurs and/or interference with the cylinder wall, combustion chamber wall, piston and the like during diffusion of the sprayed fuel.
If the above-mentioned interference occurs during a stage where atomization and diffusion of sprayed fuel are insufficient, fuel tends to adhere on the walls. As a result, it is difficult to convert the fuel into an air-fuel mixture. This obstructs combustion and degrades the engine efficiency. The related art engine has failed to solve the problems that improper direction of sprayed fuel into the combustion chamber causes.
In particular, for a rotary valve type fuel injection control valve in which a valve opening is extended in the peripheral direction, it is difficult to inject fuel in the controlled direction during fuel injection.